For comparison, normal or baryonic matter – the kind from which everything we can touch and see is made of – only accounts for less than five percent of the Universe.
Consequently, physicists have explored a wide range of theories explaining the nature of dark matter, including suggestions it is gravity leaking into our Universe from another dimension.
But not all is as it seems, thanks to new observations made by NASA’s Hubble Space Telescope.
Scientists have discovered an unusual mismatch between the theoretical models of how dark matter should be distributed in galaxy clusters and how it seems to behave.
READ MORE: NASA satellite images: Hubble images show ‘pocketful of stars’